1. Stoichiometry

2. What is stoichiometry? study of quantitative relationships in balanced chemical equation Equations represent chemical reactions

3. Physical vs. Chemical Change Physical Change = Chemical Change = Change in form/appearance Examples: Dissolving & phase changes Change in identity Change in formula representing substance

4. Evidence of a Chemical Reaction Temperature change Emission of Light Energy Change in identifying property: Color, mp, bp, density, H f, H v, c … Formation of Gas –Bubbling, odor Formation of Solid –Precipitation

5. Chemical Equations A + B  C + D Left Side = Reactants (starting materials) Right Side = Products (ending materials) “  ” read as produces/yields How do we show the physical state of the reactants & products? (s), (l), (g), (aq)

6. Law of Conservation of Matter Matter is neither created nor destroyed in chemical rxns Mass reactants = Mass productsMass reactants = Mass products Chemical bonds in reactants may break; new bonds may form to produce products # atoms of each element is “constant” # atoms each element same on both sides of equation# atoms each element same on both sides of equation

7. Coefficients in Chemical Equations in front of# in front of formulas called coefficients –apply to everything following in formula Connect microscopic world with macroscopic world –Microscopic: Coefficients represent # individual atoms/molecules –Macroscopic: Coefficients represent mole ratios! –Moles  connected to mass (MOLE MAP!)

8. Writing Chemical Equations word equationBegin with word equation –describes what happens skeleton equationNext is skeleton equation –replace names of substances with chemical formulas BalanceBalance skeleton equation –balanced equation must demonstrate law of conservation of mass

9. Equation Balancing SurveySurvey skeleton equation (left to right) –Count up # of each type of atom on reactant side –Count up # of each type of atom on product side COEFFICIENTSCOEFFICIENTS used to balance # each type atom Make successive passes checking ONE ELEMENT AT A TIMEMake successive passes checking ONE ELEMENT AT A TIME NEVER CHANGE SUBSCRIPTS IN FORMULAS –would change identity of reactant/product

10. Balanced Equations Coefficients must be in lowest possible ratios Double check your work –Do one last pass to check that all # are same on both sides Use table to keep track of # each element

11. Example 1 Fe + O 2  Fe 2 O 3 Left Side: 1 Fe and 2 O Right Side: 2 Fe and 3 O Hint: LCM of 2 and 3 = 6 Get O to 6 Fe + 3 O 2  2 Fe 2 O 3 O’s are balanced - Now balance Fe 4 Fe + 3 O 2  2 Fe 2 O 3 4 Fe and 6 O each side

12. Example 2 Na + H 2 O  NaOH + H 2 Notice: even # H’s on left, odd # on right Have to make # H’s on right even Put a 2 in front of NaOH Na + H 2 O  2 NaOH + H 2 Put a 2 in front of Na to balance Na’s 2 Na + H 2 O  2 NaOH + H 2 2 in front of H 2 O to balance O and H 2 Na + 2 H 2 O  2 NaOH + H 2

13. Example 3 AgNO 3 + MgCl 2  Mg(NO 3 ) 2 + AgCl Hint: Treat NO 3 -1 as one unit since appears on both sides of equation Balance NO 3 -1 on the left with a 2 2 AgNO 3 + MgCl 2  Mg(NO 3 ) 2 + AgCl Balance Ag’s and Cl with a 2 2 AgNO 3 + MgCl 2  Mg(NO 3 ) 2 + 2 AgCl

14. Chemical Reactions

15. Types of Reactions Synthesis Decomposition Single Replacement Double Replacement Combustion

16. Synthesis Format: A + B  C Identifying feature: 1 product only Note: A and B may be elements or compounds, C is a compound 2 Fe(s) + 3 Cl 2 (g)  2 FeCl 3 (s) CaO(s) + H 2 O(l)  Ca(OH) 2 (s)

17. Decomposition Format: AB  A + B Identifying feature: 1 reactant only Note: A & B may be elements or compounds 2 NaN 3 (s)  2 Na(s) + 3 N 2 (g) 2 NaN 3 (s)  2 Na(s) + 3 N 2 (g) NH 4 NO 3 (s)  N 2 O(g) + 2 H 2 O(g)

18. Single Replacement Format: A + BX  AX + B Identifying Feature: Element + Compound  Different Element + Different Compound 2 Li(s) + 2 H 2 O(l)  2 LiOH(aq) + H 2 (g) 2 Li(s) + 2 H 2 O(l)  2 LiOH(aq) + H 2 (g) Cu(s) + 2AgNO 3 (aq)  2Ag(s) + Cu(NO 3 ) 2 (aq)

19. Double Replacement Format: AX + BY  AY + BX Identifying feature: 2 compounds yield 2 new compounds Ca(OH) 2 (aq) + 2HCl(aq)  CaCl 2 (aq) + 2 H 2 O(l) 2 NaOH(aq) + CuCl 2 (aq)  2 NaCl(aq) + 2 NaOH(aq) + CuCl 2 (aq)  2 NaCl(aq) + Cu(OH) 2 (s) Cu(OH) 2 (s)

20. Combustion or Reaction with O 2 Format: A + O 2  B ( + C + …) Identifying feature: One of reactants is O 2 Note: A can be an element or a compound, usually more than 1 product CH 4 (g) + 2 O 2 (g)  CO 2 (g) + 2 H 2 O(g) For Regents synthesis TOPS combustion: 2 H 2 (g) + O 2 (g)  2 H 2 O(g) C(s) + O 2 (g)  CO 2 (g)

21. Identify the Reaction Type CaO + CO 2  CaCO 3CaO + CO 2  CaCO 3 2 H 2 O  2 H 2 + O 22 H 2 O  2 H 2 + O 2 NaOH + HCl  NaCl + H 2 ONaOH + HCl  NaCl + H 2 O Zn + 2 HCl  ZnCl 2 + H 2Zn + 2 HCl  ZnCl 2 + H 2 2 Mg + O 2  2 MgO2 Mg + O 2  2 MgO Mg + H 2 SO 4  MgSO 4 + H 2Mg + H 2 SO 4  MgSO 4 + H 2 2 KClO 3  2 KCl + 3 O 22 KClO 3  2 KCl + 3 O 2 AgNO 3 + NaCl  NaNO 3 + AgClAgNO 3 + NaCl  NaNO 3 + AgCl Synthesis Decomposition DR SR

22. Stoichiometry!!! Next chapter: Learn to use balanced chemical equations to predict amount of given reactant or product under certain conditions Remember: DON’T mess with the subscripts !!